Radioreceiver



April 12, 1932 w. VAN B. ROBERTS RADIORECEIVER Filed Sept. 15,

' 400/0 minus/v: Y 057E670? IMAM/75E INVENTOR ALT K VAN 5 R0 BERTS //MMW BY} fill A ORNEY Patented- Apr. 12 1932 PATENT? OFF-ICE I WALTER VANBBAAM ROBERTS, OF-IPRINGETON, NEWZJERSEY, 'ASSIGNOR TO RADIO GOR-IPORATION' OF AMERICA, A CORPORATION OF DELAWARE.

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Application filed September 15, 1928. Serial No. 306,235.

It has been shownthat a very large primary coil whose natural wavelength is greater than the longest wave length of the rangeto beMreceived, located in a certain manner with respect to a tuned secondarycircuit, gives a desirable type of variation of amplification andselectivity over a wide range of fre quencies, including the rangeutilized in ordinary radio broadcasting. However, be cause of thecapacity reactance of this coil in the range of frequencies received,its reaction upon the input circuit through the control electrode-anodecapacity of the electron discharge device utilized for amplification,dampens the input'circuit to an undesirable degree. n l p 5 1 Thisinvention has for its object the elimination of such damping and brieflythe manner in which this object is carried out, is by establishing afeed back from the output circuit of the electron discharge device ortube to the input circuit sothat the damping efiect of the large primarycoil in the output circuit, which,'at radio frequencies has'a condensiveor negative reactance,;is counteracted.-

Another important object of the, present invention is to provide a.method'of, and means for, operating a space discharge tube. amplifiercircuit having an output circuit which exercises a'd'amping effect onthe tube input-circuit, which consists in establishing,

a path betweenthe output and input circuits other than through the tubeelectrodes, and feeding energy from the output to the input circuitalong the said path so as to counteract the said damping ,elfect.

.The novel features which I believe to be characteristic of my inventionare set forth I y r in particularity in the appended claims, the

40 invention itself, however, as to both its organization and method ofoperation will best i be understood by reference to the followingdescription taken in connection with the drawings in which haveindicateddiagrammatically several circuit organizations whereby my invention maybe carried into effect.

In the accompanying drawings: 7

Fig. 1 shows a feed back circuit for eliminating the damping eifectof'the primary coil in the output circuit of a thermionic tube,

the feed back circuit including a variable condenser; V

Fig. 2 showsa modified feed back arrangement for the purposes discussedabove, where l in use is made of condenser or constant value; and,

Flg. 3 illustrates is provided a thermionic tube 1, having a.

tunable input circuit 2 and an output circuit 3 therefor. The latterhastherein a large prlmary coil 4 coupled to a tunable secondary circuit5. of tunable circuit 5 are usually mounted coaxially on a singlecylindrical element, coil a consisting of a large number of turnsbunched together and'the other coil consisting of a relatively few turnsspread out along the surface of the cylindricalelement. The numeral 6indicates the distributed natural capacity of the primary coil 4 whosenatural wave length, that is the natural Wave length of the circuitconsisting of coil 4 and its capacity 6, is greater than the longestwave length of the range to be received. Stated differently, the coil 4:is naturally resonant to a' frequency outside, and below, the frequencyrange to be received, including the range utihzed in ordinary radiobroadcasting.

It is well known that when, as in this case, the reactance of the outputcircuitis capaci-p diagrammatically and in section a primary andsecondary coil utilized Coil 4 and the coil 22 forming part to coil 9 ofinput circuit 2, and a variable condenser 10. The use of a separate coil8 permits the grounding of the rotor of condenser 10 and of the rotor ofcondenser 11 of input circuit 2.

The proper amount of feed back is obtained by varying the capacity 10simultaneously with the tuning of input circuit 2 and this may bereadily accomplished by placing the rotors of the two condensers on thesame shaft, grounding the shaft, and cutting the plate or platesof-condensers 10 so. as to give a desired capacity at each frequency towhich input circuit 2 is tuned. Feed back coil 8 is Wound as todirection as though it were part of the input coil 9. V

Primary coil 41 and its secondary 22 forming a part of tuned circuit 5,take the form shown in Fig. 3. Primary 4 consists of a relatively largenumber'of turns bunchedtogether on cylindrical member 20. The turns ofsecondary 22 are spread out along the surface of cylinder 20 as shown.

The remaining portions of the apparatus of Fig. 1 are self-explanatory.

In Fig. '2, I have shown another way of carryin out'my invention. Inthis modification a xed condenser 11' is utilized in the feedbackcircuit in connection with a tapped input coil 12, the lower portion 13of the coil 12 formin the other part of the feed back circuit. filelatter is, of course, magnetically coupled to the portion of the coil 12included 1n the tunable input circuit 2.

I have found that the use of a fixed value of capacity '11 gives goodresults especially if the value is so chosen that there is a slightexcess of regeneration at the upper or high frequency end of the rangeto which the receiver may be tuned.

The choice of either of the modifications shown in either Figures 1 or 2depends upon the manufacturing advantages desired. Thus, Fig. 1 permitsthe grounding of the rotor of the input tuning condenser and Fig. 2offers as its manufacturing advantage a simplified structure because thefeed back coil may be simply an extension of the input coil. 7 I

As indicated in the drawings the tuning condensers-may be coupledtogether so as to provide a uni-control arrangement, and as shown inFig. 1, condenser 10 may also be included in the uni-control system.

- While I have indicated and described several systems for carrying myinvention into effect, it will be apparent to one skilled in the artthat my invention is by no means limited to the particular organizationsshown and de scribed, but that many modifications in the circuitarrangements, as wellas in the apparatus employed, may be made withoutdeparting from the scope of my invention as set forth in theappendedclaims.

Having thus described my invention what I claim is 1. A tuned radiofrequency amplifier having an input circuit and having an output circuitwhose reactance is condensive, said output circuit delivering power to atuned circuit, and means for feeding back power to the input circuit soas to eliminate the damping effect on said input circuit of the capacityreactance of said output circuit.

2. In combination, an output circuit of an electron discharge devicewhose 'reactance is negative, the output circuit feeding power to atuned secondary circuit, a feed back coil and current limiting condenserconnected in series between the anode and cathode of the electrondischarge device, said feed back coil being magnetically coupled to theinput circuit of the device.

3. In an amplifier, a thermionic tube, a tunable input circuit therefor,an output circuit therefor including a coil whose inductance is so greatthat the output current of the tube tends to flow mostly through thenatural capacity of the coil and other capacities shunting said coil,causing a di1mping efiect on the input circuit of said tube, and meansincluding a-path between the out ut andin put circuits forcounteracting. said damping effect.

4. In an amplifier, a thermionic tube, a tunable in ut circuit therefor,an output circuit there or comprising 8,0011 whose inductance is sogreat that the output current of the tube tends to flow through thenatural capacity of the coil causing a damping eifecton the inputcircuit of said tube, and meansfor counteracting said dumping efi'ect,saidmeans comprising an inductance and a condenser in series, said lastmentioned inductance being magnetically coupled to the input circuit ofsaid tube.

5. The method of operating a space discharge. tube amplifier having anoutput circuit with a'negative reactance which consists in feeding backenergy from the output circuit tothe tube inputcircuit through a, athother than the inter-electrode coupling of the tube, to counteract theeffect of said negative reactance on the input circuit.

6. The method of operating a multi-electrode amplifier tube having anoutput circuit which exerci'ses 'a damping efiect upon the tube inputcircuit, the method consisting in establishing a path between the outputand input circuits other than through the tube electrodes, and feedingenergy-from the output to the input circuit along the said path so as tocounteract said damping effect.

7. The'method of operating an amplifier circuitwhich includes amulti-electrode space discharge tubehaving an output circuit including areactance naturally resonant to a frequency below the broadcast rangeand which exercises a damping effect on the tube input circuit, themethod consisting in regeneratively coupling the output circuit to theinput circuit, and feeding back energy from'the output to the inputcircuit to councises a damping effect on the said input cir-- cuit, anda path including a pair of reactances between the output and inputcircuits for counteractingsaid damping efie'ct, one of said reactancesbeing variable.

10. In an amplifier, a thermionic tube, a tunable input circuit thereforincluding a variable condenser, an. output circuit for the tube having anegative reactance which has a damping effect on the said input circuit,a subsequent tuned ,circuit'coupled to said output circuit, saidsubsequent circuit includinga variable condenser, and a path between theoutput circuit and the first tuned input circuit for feeding back energyto counteract said damping effect, said path including a variablecondenser, the rotors of all ofsaid condensers being grounded andmechanically connected for simultaneous movement.

11. In an amplifier, a spaced discharge tube including a tunable inputcircuit and an output circuit, a coil in said output circuit naturallyresonant to a frequency outside a predetermined frequency range andcausing a degenerative eifect on said input circuit, and a path betweenthe output and input circuits for counteracting said effect.

12. A timed radio frequency amplifier tube having an input and outputcircuit, the output circuit including a reactance having a degenerativeefi'ect on the input circuit, a path between the output and inputcircuits for regeneratively counteracting the said effect, said pathincluding a fixed reactance, and the value of said reactance being suchthat excess c of regeneration resultsat the upper end of:

the frequency range towhich the amplifier may be tuned.

13. A tuned radio frequency amplifier tube having an'input and outputcircuit, the out put circuit including a reactance having a degenerativeeffect on the input circuit, a path between the output and inputcircuits for regeneratively counteracting the said effect, said pathincluding a fixed capacity, and the value of said capacity being suchthat excess of regeneration results at the upper end of the frequencyrange to which the amplifier maybe tuned.

14. A tuned radio frequency amplifier tube having an input and outputcircuit,'the output circuit including a coil having a degenerativeeffect on the input circuit, a path be tween the output and inputcircuits for regeneratively counteracting the said effect, said pathincluding a fixed capacity, and the value of said capacity being suchthat excess of regeneration results at the upper end of the frequencyrange to which the amplifier may be tuned.

WALTER VAN BRAAM ROBERTS.-

DISCLAIMER 1,853,178.Walter ran Braam Roberts, Princeton, N. J.RADIoREoErvER. Patent dated April 12, 1932. Disclaimer filed December21, 1932, by the assignee, Radio Corporation of America. Hereby entersthis disclaimer to the said claims of said Letters Patent which are inthe following words, to Wit:

1. A tuned radio frequency amplifier having an input circuit and havingan output circuit whose reactance is condensive, said output circuitdelivering power to a tuned circuit, and means for feeding back power tothe input circuit so as to eliminate the damping effect on said inputcircuit of the, capacity reactance of said output circuit.

2. In combination, an output circuit of an electron discharge deviceWhose reactance is negative, the output circuit feeding power to a tunedsecondary circuit, a feed back coil and current limiting condenserconnected in series between the anode and cathode of the electrondischarge device, said feed back coil being magnetically coupled to theinput circuit of the device.

3. In an amplifier, a thermionic tube, a tunable input circuit therefor,an output circuit therefor including a coil whose inductance is so greatthat the output current of the tube tends to flow mostly through thenatural capacity of the coil and other capacities shunting said coil,causing a damping effect on the input circuit of said tube, and meansincluding a path between the output and input circuits for counteractingsaid damping effect.

4. In an amplifier, a thermionic tube, a tunable input circuit therefor,an output circuit therefor comprising a coil whose inductance is sogreat that the output current of the tube tends to flow through thenatural capacity of the coil causing a damping efiect on the inputcircuit of said tube, and means for counteracting said damping efiect,said means comprising an inductance and a condenser in series, said lastmentioned inductance being magnetically coupled to the input circuit ofsaid tube.

5. The method of operating a space discharge tube amplifier having anoutput circuit with a negative reactance which consists in feeding backenergy from the output circuit to the tube input circuit through a pathother than the inter-electrode coupling of the tube, to counteract theeffect of said negative reactance on the input circuit.

6. The method of operating a multi-electrode amplifier tube having anoutput circuit which exercises a damping effect upon the tube inputcircuit, the method consisting in establishing a path between the outputand input circuits other than through the tube electrodes, and feedingenergy from the output to the input circuit along the said path so as tocounteract said damping effect.

7. The method of operating an amplifier circuit which includes amulti-electrode space discharge tube having an output circuit includinga reactance naturally resonant to a frequency below the broadcast rangeand which exercises a damping eflect on the tube input circuit, themethod consisting in regeneratively coupling the output circuit to theinput circuit, and feeding back energy from the output to the inputcircuit to counteract said damping effect.

8. A tuned radio frequency amplifier having an input circuit and anoutput circuit, the latter having a negative reactance, and exercising adamping effect on the input circuit, and a path between the output andinput circuit for feeding back energy to the latter to eliminate saiddamping effect, said path including an adjustable reactance.

9. In an amplifier, a space discharge device, an input circuit therefor,an output circuit therefor including a reactance which exercises adamping effect on the said input circuit, and a path including a pair ofreactances between the output and input circuits for counteracting saiddamping effect, one of said reactances being variable.

11. In an amplifier, a space discharge tube including a tunable inputcircuit and an output circuit, a coil in said output circuit naturallyresonant to a frequency outside a predetermined frequency range, andcausing a degenerative effect on said input cifrcuit, and a path betweenthe output and input circuits for counteracting said e ect.

[Ofictal Gazette January 17, 1.933.]

